Chad Meyer (Vicasso)
I wish this was possible, but unfortunately Salesforce platform contraints don't allow us to control this. If you have a contact (or lead) associated with each case, which generally should be the case, this shouldn't ever be an issue for customer facing emails.That said, should Salesforce relax this constraint, we'll strongly consider making this change.Technical explaination:When sending an email with a template, a target object ID (contact, lead, user) is required to ensure merge fields are populated. The target object is automatically a To recipient and can't be moved to CC or BCC.https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_email_outbound_single.htm"setTargetObjectId(targetObjectId)Required if using a template, optional otherwise. The ID of the contact, lead, or user to which the email will be sent. The ID you specify sets the context and ensures that merge fields in the template contain the correct data."